torrefaction of biomass

1. TORREFACTION OF
BIOMASS
PRESENTED BY
KULWINDER KAUR
1

2. BACKGROUND
(For coffee and tea making) 2

3. Structure of Biomass
• Biomass is any organic materials derived from
plants or animals
,
3
Lignocellulosic
Non-
Lignocellulosic
cellulose
hemicellulose
lignin
Protein, starch and
fat
E.G crop

4. Composition of lignocellulosic Biomass
• Lignin
C-O-C and C-C linkages
Decompose at wide range of temperature (450-900 °C)
• Hemicellulose
acetyl- and methyl substituted groups
lower degree of polymerization
significant loss of mass yield
• Cellulose
long chain intra-molecular and inter-molecular hydrogen bonds
Hygroscopic nature of raw biomass
4

5. 5
Composition of different biomass

6. Issues with woody biomass
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 High moisture content (45-60%,wb)
 Low bulk and energy density
 Poor grindability
 Hygroscopic nature
 High oxygen content
 High alkali metal content
 Heterogeneity
Torrefaction can address most of these issues
to a reasonable extent.

7. TORREFACTION
(keep, upgrade and expose)
7
A thermo-chemical process in an inert or limited oxygen environment
where biomass is slowly heated within a temperature range of 200-300 C
and retained there for a stipulated time such that it results near
complete degradation of its hemicelluloses while maximizing mass and
energy yield of solid products.

8. Torrefaction effect on lignocellulosic biomass
8

9. Higher humidity
Lower HV
Higher O/C ratio
Hydrophillic
Lower Grindibility
Non uniform properties
Torrefaction at
200-300°C
in inert
atmosphere
Lower humidity
Higher HV
Lower O/C ratio
Hyrophobicity
Higher Grindibility
Uniform Properties
Non Torrified Biomass Torrified Biomass

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Mass And Energy Yield

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Products formed during torrefaction of biomass

12. Types of Torrefaction
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Dry
torrefaction
Inert gas
250-300°C
80
minutes
Hydrothermal
Torrefaction
Water/
steam
180-260°C
4.6 Mpa
5 minutes
Dry biomass to
water ratio= 1:6

13. Difference between dry and wet
torrefaction
13

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15. Wet torrefaction
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16. wet torrefaction
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• Biomass containing high
amounts of moisture, typically
above 50% (wet basis)
• Pretreat animal manures,
human waste, sewage sledges,
municipal solid waste,
aquaculture residues and
microalgae
• Increase the energy density of
biomass by up to 36% above
• Reduction in corrosion
• Relatively short period (5
minutes) of residence time
Advantages Disadvantages
• Require high capacity
water reactor
• Expensive due to
pressurized reactor
• Distilled water is required
• Output liquid contains
alkali that cause
environmental hazards.

17. Torrefaction
17
Degradation of the biomass during the dry
torrefaction, takes place mainly through the
drying and devolatilization process.
Drying
Process of removing a
surface and bound water
from the raw biomass.
Drying is classified as a non-
reacting and a reactive
process.
Devolatilization
Process of removing oxygen
and volatile content of
biomass at above 200 °C

18. Heating stages of Dry Torrefaction Process
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ambient 100°C 100°C 200°C 300°C ambient

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20. Schematic machine of torrefaction
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21. TYPICAL TORREFACTION PROCESS FLOW
21Source: Energy research center NETHERLAND

22. Changes in Biomass
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23. Parameters affecting Torrefaction Process
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• Reaction temperature (200-300°C)
• Residence time (< 30min)
• Heating rate (<50°C/min)
• Absence of oxygen (<14%)
• Ambient pressure (1 atm)
• Feedstock moisture content ( 30-60%,wb)
• Feedstock particle size (1-2mm)

24. Torrefaction classification and torrefaction products
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Classification Light Mild Severe
Temperature(℃) 200-235 235-275 275-300
Hemicellulose Mild Mild to severe Severe
Cellulose Slight Slight to mild Mild to severe
Lignin Slight Slight Slight
Liquid color Brown Brown dark Black

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Length and the
rotational speed of the
screw in a screw type
reactor, and the belt
speed in the conveyer
belt reactor
Lower solid product
yield due to more
devolatilization
Volume requirement
of the reactor
Carbon loss Increases
due to formation of CO
and Volatile and
decrease the
torrefaction efficiency
Residence time

26. Heating rate
(<50°C/min)
26
Reduction of the number
of secondary reactions
Energy yield of liquid
pyrolysis is higher when
the heating rate is also
higher
More flue gas and lower
sold product yield
Endangering the safety
of the unit due to
increase the temperature
of the product
Oxygen content
(<14%)

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Non uniform
heat
distribution
Poor quality
of end
product
Difficulty in
volatile
diffusion
Large
particles
(5-25mm)
Mass loss
increases
High heat
transfer
Small
particles
(<1mm)
Feed Size

28. Classification of Torrefaction Reactor
Directly Heated
• Convective reactor
• Fluidized bed reactor
• Hydrothermal reactor
• Microwave reactor
Indirectly Heated
• Rotating drum
• Screw conveyer reactors

29. Torrefaction Reactor
Convective Reactor (Fixed, moving and entrained)
42mm
1.6mm
11 lit/min

30. Fluidised Bed Reactor
228 mm
21 lit/min

31. Rotating Drum Torifier

32. Screw shaft torrifier
32

33. Microwave Torrefier

34. S.no Characteristics Value Reference
1 Moisture Content: 1-6 % Bergman and Kiel, (2005).
2 Density 180–300 kg/m3 Bergman and Kiel, (2005).
3 Grindibility Better Arias et al., (2008).
4 Power reduction 70-90% Bergman and Kiel, (2005).
5 Particle size distribution uniform Phanphanich and Mani
(2011)
6 Sphericity 0.48–0.62%
increases
Phanphanich and Mani
(2011)
7 Bulk and particle densities increases Esteban and Carrasco,
(2006)
8 Palletabilty increases Lehtikangas, (1999).
9 Carbon content 48.6–54.3% Bridgeman et al. (2008)
10 Hydrogen content 6.8–6.1% Bridgeman et al. (2008)
11 Nitrogen content 0.3– 0.1% Bridgeman et al. (2008)
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Physical properties and chemical composition of torrefied biomass

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Benefits
Improves the physical
characteristics
Homogeneous
solid fuel
High energy
content
Low Moisture
content
Hydrophobic
Ease of Transport
and handling
Negligible biological
activities
Low O/C ratio
Smoke free
compound
Pelletization easier
Torrefied pellets
have more strength
Economical
Limitations
Low vol. density
enhancement
Corrosive deposits
on boiler tubes
Limited knowledge
on process
No commercial
torrefaction unit

36. APPLICATION/MARKET FOR TORREFIED BIOMASS
• Residential and commercial heating
• Power generation
 Biomass Co-firing in large scale coal-fired power plants
• Waste water treatment
 As an activated carbon – an adsorbent made from biomass,
to remove the organic or inorganic substances from the
liquid and gases.
• Metal extraction
 As a reducing agent to replace the coking coal
• Biofuel production,
 Lower moisture and O/C ratio, the quality of the bio-oil can
be improved using the torrefied biomass in fast pyrolysis.
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37. • Gasification:
 Torrefied biomass rather than raw biomass as a feedstock is
expected to improve the gasification efficiency
 Lower the tar formation
• Pelletilization:
 Increased the volumetric energy density (40-200kJ·m-3 to
600-1400kJ·m-3 )
 Easy to handle
 Reducing the transportation cost
 Decreasing the moisture content
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38. Future Perspectives and Research
Developments
• Studies are required that investigate such
parameters to find the best set to obtain an ideal
torrefied biomass sample.
• Torrefaction must be conducted intelligently, with
controlled costs, and is entirely directed towards
the progress and success of the marketing.
• The material produced should be completely
homogeneous, with respect to the degree of
torrefaction, and preferably dark brown (not
over-torrefied), to allow sufficient yield and to
facilitate densification.
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